Mirror device, scanning laser device and scanning display including same mirror device, and method for manufacturing mirror device

ABSTRACT

A mirror device includes a frame body, a shaft member provided inside the frame body and connected to the frame body at both end portions, and a reflection member fixed to the shaft member and provided so as to be capable of swinging around an axis of the shaft member. The reflection member has a base portion provided along an axial direction of the shaft member and a reflection portion provided on the base portion. The base portion has a three-dimensional uneven structure including a bottom wall portion having a main surface provided along the axial direction of the shaft member and a plurality of side wall portions extending from the bottom wall portion on the side opposite to the reflection portion.

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed on U.S. patent application Ser. No. 16/549,546,filed Aug. 23, 2019, the content of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a mirror device, a scanning laserdevice and a scanning laser display including the mirror device, and amethod for manufacturing a mirror device.

The present application claims priority based on U.S. patent applicationSer. No. 16/549,546 filed in the United States of America on Aug. 23,2019, and the content thereof is incorporated herein by reference.

Description of Related Art

In the related art, there are scanning laser devices including a mirrordevice such as a micro mirror. Micro mirrors are also referred to asscanners and are applied to mobile devices such as mobile displays dueto their simple and small structures.

In recent years, for example, as wearable devices, head-mounted virtualreality (VR)/augmented reality (AR)/mixed reality (MR) displays havebeen attracting attention, and active research and development thereofhas been underway. In order to produce more realistic VR/AR/MR, as animage projection system that is used for displays, small-sized andlightweight high-resolution scanning laser devices are required, andmicro mirrors capable of realizing small-sized and lightweighthigh-resolution scanning laser devices are drawing attention.

A determinant of the resolution of scanning laser devices is theperformance of micro mirrors, and the resolution varies with theoperation frequencies, rotation angles (optical scanning angles), anddiameters of micro mirrors. A micro mirror has a structure in which asmall-sized mirror is supported by a twisted spring, and, generally, theabove-described three parameters of the operation frequency, therotation angle, and the diameter have a trade-off relationship. Forexample, an increase in the operation frequency while keeping thediameter of a mirror constant leads to an increase in the thickness ofthe mirror that is necessary to suppress the dynamic deformation of themirror. As a result, the diameter of a torsion bar is increased in orderto suppress a decrease in the operation frequency attributed to theincrease in the thickness of the mirror, and furthermore, thepermissible break rotation angle of the torsion bar decreases.Therefore, it is difficult to improve all of the above-describedparameters, and it is not easy to improve the resolution of scanninglaser devices.

A requirement for an increase in the resolution of scanning laserdevices is intensifying in association with an increase in theresolution of other display devices such as liquid crystal displays. Forexample, in the case of realizing a definition as high as the resolutionof HDTVs, a horizontal resolution of 1,920, a vertical resolution of1,080, a horizontal scanning frequency of 36 kHz, and a product of anoptical scanning angle and a diameter of 90 degree·mm are required.

Hitherto, the present inventors have strived to increase the resolutionusing a variety of methods. For example, as a mirror device that is usedfor scanning laser displays, a micro mirror having a mirror platesupported by a frame portion through a torsion bar so as to be capableof swinging is disclosed (for example, Non-Patent Document 1). Thismicro mirror has a diameter of 420 μm and has realized an operationfrequency of 24.5 kHz and an optical scanning angle of 5.14 degrees.

[Non-Patent Document 1] Chu Houng Manh et al., Vacuum operation ofComb-drive micro display mirrors, J. Micromech Microeng. 19 (2009),105018 (8 pp)

SUMMARY OF THE INVENTION

However, the configurations of the related art are not favorable enoughto realize an additional increase in the resolution.

An object of the present disclosure is to provide a mirror devicecapable of realizing a higher resolution than in the related art, ascanning laser device and a scanning laser display including the mirrordevice, and a method for manufacturing a mirror device.

According to a first aspect of the present disclosure, a mirror deviceincludes

a frame body,

a shaft member provided inside the frame body and connected to the framebody, and

a reflection member fixed to the shaft member and provided so as toswing around an axis of the shaft member,

the reflection member has a base portion provided along an axialdirection of the shaft member and a reflection portion provided on thebase portion, and

the base portion has a three-dimensional uneven structure including abottom wall portion having a main surface provided along the axialdirection of the shaft member and a plurality of side wall portionsextending from the bottom wall portion on a side opposite to thereflection portion.

The ratio of the height to the thickness of the side wall portion ispreferably 20 or more and 100,000 or less.

The base portion is preferably formed of an ALD layer and/or an MLDlayer.

The plurality of side wall portions may be formed of a plurality of finsdisposed at intervals in the axial direction of the shaft member.

The base portion may include the bottom wall portion, a first side wallportion group formed of a plurality of pairs of first side wall portionsextending in a first direction in a plan view of the base portion, and afirst upper wall portion group formed of a plurality of first upper wallportions that couples the pairs of first side wall portions.

In addition, the base portion may further include a pair of second sidewall portions disposed so as to surround the first side wall portiongroup in a plan view of the base portion and a second upper wall portionthat couples the pair of second side wall portions and is connected tothe first upper wall portion group.

A through hole may be provided in at least one of the first upper wallportion and the second upper wall portion,

the bottom wall portion, the pair of first side wall portions, and thefirst upper wall portion may define a first hollow portion, and

the bottom wall portion, the pair of second side wall portions, and thesecond upper wall portion may define a second hollow portion.

In addition, the base portion may include the bottom wall portion, afirst side wall portion group formed of a plurality of pairs of firstside wall portions extending in a first direction in a plan view of thebase portion, and a third side wall portion group formed of a pluralityof pairs of third side wall portions that extends in a second directionintersecting the first direction and couples the pairs of first sidewall portions.

The first side wall portion group and the third side wall portion groupmay be disposed in a grid shape in a plan view of the base portion.

The base portion may further include a third upper wall portion groupformed of a plurality of third upper wall portions that is defined bytwo adjacent first side wall portions and two adjacent third side wallportions in a plan view of the base portion,

one or a plurality of through holes may be provided in the third upperwall portion, and

the bottom wall portion, the pair of first side wall portions, the pairof third side wall portions, and the third upper wall portion may definea third hollow portion.

In addition, the base portion may include the bottom wall portion, afirst side wall portion group formed of a plurality of pairs of firstside wall portions extending in a first direction in a plan view of thebase portion, a third side wall portion group formed of a plurality ofpairs of third side wall portions extending in a second directionintersecting the first direction, and a fourth side wall portion groupformed of a plurality of pairs of fourth side wall portions extending ina third direction intersecting both the first direction and the seconddirection.

The first side wall portion group, the third side wall portion group,and the fourth side wall portion group may form a truss-shaped structurein a plan view of the base portion.

The base portion may further include a fourth upper wall portion that isdefined by the first side wall portion group, the third side wallportion group, and the fourth side wall portion group in a plan view ofthe base portion,

one or a plurality of through holes may be provided in the fourth upperwall portion,

the bottom wall portion, the pair of first side wall portions, and afirst portion of the fourth upper wall portion may define a firstportion of a fourth hollow portion,

the bottom wall portion, the pair of third side wall portions, and asecond portion of the fourth upper wall portion may define a secondportion of the fourth hollow portion, and

the bottom wall portion, the pair of fourth side wall portions, and athird portion of the fourth upper wall portion may define a thirdportion of the fourth hollow portion.

The base portion may further include a fifth side wall portion groupthat couples the first side wall portions adjacent to each other in avoid portion between one of a pair of first side wall portions formingthe first side wall portion group and one of another pair of first sidewall portions.

In addition, the first side wall portion group and the fifth side wallportion group may form a truss-shaped structure in a plan view of thebase portion.

The mirror device may further include a pair of comb tooth portionsprovided in any of the frame body and the shaft member.

The base portion may be formed of a metal oxide, and the metal oxide maybe Al₂O₃.

According to a second aspect of the present disclosure, a scanning laserdevice includes a laser light source, the mirror device, and a drivingmechanism configured to drive the mirror device.

According to a third aspect of the present invention, a scanning displayincluding the scanning laser device may be provided.

According to a fourth aspect of the present disclosure, a method formanufacturing a mirror device includes

a step (A1) of carrying out anisotropic deep reactive ion etching (RIE)on a device layer of an SOI wafer and forming in uneven portionextending in a direction perpendicular to a main surface of the SOIwafer,

a step (B1) of conformally depositing a first layer on the unevenportion by ALD and/or MLD,

a step (C1) of forming a through hole or a through groove in the firstlayer formed on an upper surface of the uneven portion by anisotropicetching,

a step (D1) of patterning the first layer formed on a handle layer ofthe SOI wafer by anisotropic etching,

a step (E1) of removing the handle layer of the SOI wafer by anisotropicetching to expose an oxide layer of the SOI wafer,

a step (F1) of removing the oxide layer by anisotropic RIE to expose alower surface of the uneven portion,

a step (G1) of conformally depositing a second layer on the first layerand the lower surface of the uneven portion by ALD and/or MLD,

a step (H1) of removing the second layer formed in the through hole orthe through groove by anisotropic etching to form a through hole or athrough groove in the first layer again,

a step (I1) of depositing a metal on the second layer from the handlelayer side of the SOI wafer to form a reflection portion on the secondlayer, and

a step (J1) of removing the uneven portion of the device layer throughthe through hole or the through groove by isotropic RIE.

According to a fifth aspect of the present disclosure, a method formanufacturing a mirror device includes

a step (A2) of depositing a first layer on a device layer of an SOIwafer by ALD and/or MLD and depositing a second layer on a handle layerof the SOI wafer,

a step (B2) of patterning the first layer by anisotropic etching toform, on the device, a plurality of linear protrusion portions having aplurality of circular recess portions linearly arranged on an uppersurface and a plurality of linear recess portions that allows the devicelayer to be exposed between the plurality of linear protrusion portions,

a step (C2) of patterning the second layer on the handle layer byanisotropic etching,

a step (D2) of carrying out masking on the linear recess portions atpredetermined intervals and carrying out anisotropic deep RIE (reactiveion etching) on the exposed device layer on which the masking is notcarried out to form an uneven precursor including a plurality of firstgroove portions extending in a direction perpendicular to a main surfaceof the SOI wafer,

a step (E2) of conformally depositing a third layer on the unevenprecursor by ALD and/or MLD,

a step (F2) of removing parts of the third layer deposited on uppersurfaces of portions on which the masking is carried out in the unevenprecursor by anisotropic etching,

a step (G2) of carrying out anisotropic deep RIE on the uneven precursorexposed by the removal of the parts of the third layer and removing theportions exposed by the removal of the parts of the third layer in theuneven precursor to form an uneven portion including a plurality ofsecond groove portions extending in the direction perpendicular to themain surface of the SOI wafer,

a step (H2) of conformally depositing a fourth layer on the unevenportion by ALD and/or MLD.

a step (I2) of removing the handle layer of the SOI wafer by anisotropicetching to expose an oxide layer of the SOI wafer,

a step (J2) of removing the oxide layer by anisotropic RIE to exposelower surfaces of the uneven portion,

a step (K1) of conformally depositing a fifth layer on the lowersurfaces of the uneven portion by ALD and/or MLD,

a step (L2) of forming through holes or through grooves at positionscorresponding to the plurality of circular recess portions in the firstlayer by anisotropic etching,

a step (M2) of depositing a metal on the fifth layer from the handlelayer side of the SOI wafer to form a reflection portion on the fifthlayer, and

a step (N2) of removing the uneven portion through the through holes orthe through grooves by isotropic RIE.

According to the present disclosure, it is possible to realize a higherresolution than in the related art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a configuration of amirror device according to a first embodiment of the present disclosure.

FIG. 2 is a partial enlarged side view of the mirror device of FIG. 1.

FIG. 3 is a perspective view schematically showing a configuration of amirror device according to a second embodiment of the presentdisclosure.

FIG. 4A is a plan view of the mirror device of FIG. 3, and FIG. 4B is across-sectional view in a direction of a line I-I in FIG. 4A.

FIG. 5 is a partial enlarged image of the mirror device of FIG. 3.

FIG. 6A to FIG. 6C are step views showing an example of a method formanufacturing the mirror device of FIG. 3.

FIG. 7 is a schematic view for showing an ALD method that is used at thetime of manufacturing the mirror device.

FIG. 8A to FIG. 8C are step views showing an example of a method formanufacturing the mirror device of FIG. 3.

FIG. 9A to FIG. 9C are step views showing an example of a method formanufacturing the mirror device of FIG. 3.

FIG. 10A to FIG. 10C are step views showing an example of a method formanufacturing the mirror device of FIG. 3.

FIG. 11A is a partial plan view showing a modification example of a baseportion of FIG. 3. FIG. 11B is a cross-sectional view in a direction ofa line II-II of FIG. 11A. FIG. 11C is a cross-sectional view in adirection of a line III-III of FIG. 11A.

FIG. 12A is a partial plan view showing another modification example ofthe base portion of FIG. 3. FIG. 12B is a cross-sectional view in adirection of a line IV-IV of FIG. 12A. FIG. 12C is a cross-sectionalview in a direction of a line V-V of FIG. 12A.

FIG. 13A is a partial plan view showing another modification example ofthe base portion of FIG. 3, and FIG. 13B is a cross-sectional view in adirection of a line VI-VI of FIG. 13A.

FIG. 14A is a plan view showing a modification example of the mirrordevice of FIG. 3. FIG. 14B is a cross-sectional view in a direction of aline VII-VII of FIG. 14A. FIG. 14C is a cross-sectional view in adirection of a line VIII-VIII of FIG. 14A.

FIG. 15A is an electron microscope image of the mirror device of FIG.14A, and FIG. 15B is a partial cross-sectional image of FIG. 15A.

FIG. 16A is a view showing three-dimensional mapping obtained bycarrying out surface profiling using a white-light interferometer in themirror device of FIG. 14A.

FIG. 16B is a graph showing the height distribution along a crosssection in a direction of a line VIIII-VIIII of FIG. 16A.

FIG. 17A is a plan view schematically showing a configuration of amirror device according to a third embodiment of the present disclosure,and FIG. 17B is a partial cross-sectional perspective view in adirection of a line X-X in FIG. 17A.

FIG. 18 is an electron microscope image showing an example of aconfiguration of a plurality of fifth side wall portions in FIG. 17B.

FIG. 19A to FIG. 19D are step views showing an example of a method formanufacturing the mirror device of FIG. 17.

FIG. 20A to FIG. 20C are step views showing the example of the methodfor manufacturing the mirror device of FIG. 17.

FIG. 21A to FIG. 21C are step views showing the example of the methodfor manufacturing the mirror device of FIG. 17.

FIG. 22A to FIG. 22F are plan views showing the example of the methodfor manufacturing the mirror device of FIG 17.

FIG. 23A to FIG. 23D are plan views showing the example of the methodfor manufacturing the mirror device of FIG. 17A.

FIG. 24 is a view showing the details of steps from FIG. 22E to FIG.23B.

FIG. 25 is an electron microscope image showing a modification exampleof a configuration of the base portion of FIG. 18.

FIG. 26 is a schematic view showing an example of a configuration of ascanning laser device according to a fourth embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to drawings.

FIG. 1 is a perspective view schematically showing a configuration of amirror device according to a first embodiment of the present disclosure,and FIG. 2 is a partial enlarged side view of the mirror device ofFIG. 1. In some of the drawings to be used in the following description,a characteristic portion is shown in an enlarged manner for conveniencein order to facilitate the understanding of the characteristic, and theshape, dimensional ratios, and the like of individual configurationalelements are not limited to those shown in the drawings.

In the respective drawings, a D1 direction refers to a length directionof the mirror device. A D2 direction refers to the width direction ofthe mirror device. A D3 direction refers to the height direction of themirror device.

As shown in FIG. 1, a mirror device 1A includes a frame body 10A, ashaft member 20A provided inside the frame body 10A and connected to theframe body 10A, and a reflection member 30A fixed to the shaft member20A and provided so as to be capable of swinging around an axis of theshaft member 20A.

The frame body 10A in the present embodiment is disposed along anin-plane direction that is regulated by the D1 direction and the D2direction and has a substantially rectangular shape in a plan view ofthe mirror device 1A. The frame body 10A is, for example, formed of asilicon (Si) layer, formed of a laminate of a silicon layer and an oxidelayer, or formed of a germanium (Ge) layer. The silicon layer is formedof, for example, single-crystal silicon (Si), and the oxide layer isformed of, for example, silicon oxide (SiO₂ or the like).

The shaft member 20A has a first shaft portion 20Aa that couples,between a pair of facing frame portions 10Aa and 10Ab, the frame portion10Aa and the reflection member 30A and a second shaft portion 20Ab thatcouples the frame portion 10Ab and the reflection member 30A. The shaftmember 20A is integrally formed with, for example, a base portion 31A,described below, of the reflection member 30A. The shaft member 20A has,for example, a substantially rectangular shape in a cross-sectional viewin the width direction (D2 direction).

The shaft member 20A is, for example, formed of a silicon (Si) layer,formed of a laminate of a silicon layer and an oxide layer, or formed ofa germanium (Ge) layer. The silicon layer is formed of, for example,single-crystal silicon or polycrystal silicon, and the oxide layer isformed of, for example, silicon oxide (SiO₂ or the like).

As shown in FIG. 2, the reflection member 30A has a base portion 31Aprovided along the axial direction (D1 direction) of the shaft member20A and a reflection portion 32A provided on the base portion. This baseportion 31A has a three-dimensional uneven structure including an upperwall portion 311A having a main surface 311Aa provided along the axialdirection (D1 direction) of the shaft member 20A and a plurality of sidewall portions 312A, 312A, . . . extending from the upper wall portion311A on the side opposite to the reflection portion 32A. In order tofacilitate the understanding of the characteristic of the reflectionmember 30A, FIG. 1 and FIG 2 show the upper wall portion 311A in a stateof being positioned on the upper side, however, in a state in which themirror device 1A is rotated 180 degrees around the shaft member 20A as arotation center, the upper wall portion 311A forms a bottom wallportion.

The base portion 31A is a member that supports the reflection portion32A and swings clockwise or counterclockwise due to stress generated bythe torsion of the shaft member 20A. As described above, this baseportion 31A is integrally formed with the shaft member 20A. The baseportion 31A is substantially a cuboid and has, for example, a length (D1direction) of 100 μm or more and 5,000 μm or less, a width (D2direction) of 100 μm or more and 5,000 μm or less, and a height (D3direction) of 10 μm or more and 2,000 μm or less. As an example, thebase portion 31A is 2,000 μm in length, 2,000 μm in width, and 679 μm inheight

The base portion 31A is preferably formed of an ALD layer and/or an MLDlayer. The ALD layer refers to a layer formed by atomic layerdeposition, and the MLD layer refers to a layer formed by molecularlayer deposition. The ALD/MLD layers can be specified as an object fromthe crystal state or the like and can be clearly differentiated fromlayers formed using other methods such as CVD or spin coating. When thebase portion 31A is formed of the ALD layer and/or the MLD layer, it ispossible to reliably realize a high aspect ratio of the side wallportion 312A.

The base portion 31A can be formed of any of a metal oxide and a metalnitride and is preferably formed of a metal oxide. The metal oxide isnot particularly limited and is, for example, aluminum oxide (Al₂O₃).The metal nitride is, for example, silicon nitride (SiN or Si₃N₄).

The upper wall portion 311A has a substantially rectangular shape in aplan view of the base portion 31A and is formed across all of the baseportion 31A in the plan view of the base portion 31A. The upper wallportion 311A has, for example, a thickness (D3 direction) of 20 nm ormore and 500 nm or less. As an example, the thickness of the upper wallportion 311A is 50 nm. The reflection portion 32A is formed on one mainsurface 311Aa of the upper wall portion 311A, and the plurality of sidewall portions 312A, 312A, . . . is provided on the other main surface311Ab.

The side wall portions 312A are disposed perpendicular to the upper wallportion 311A and have a substantially rectangular shape in a side viewin the D1 direction (FIG. 1). The side wall portion 312A has, forexample, a length (D2 direction) of 100 μm or more and 5,000 μm or less,a width (D3 direction) of 10 μm or more and 2,000 μm or less, and athickness (D1 direction) of 20 nm or more and 500 nm or less. Inparticular, the ratio of the height to the thickness of the side wallportion 312A (the aspect ratio of a D3-direction dimension to aD1-direction dimension) is 20 or more and 100,000 or less, preferably100 or more and 10,000 or less, more preferably 1,000 or more and 10,000or less, particularly preferably 5,000 or more and 7,000 or less, andthe side wall portion has a characteristic high aspect ratio. As anexample, the side wall portion 312A is 2,000 μm in length (D2direction), 679 μm in width (D3 direction), and 100 nm in thickness (D1direction). At this time, the aspect ratio of the side wall portion 312Ais 679/0.1=6,790.

In the present embodiment, the plurality of side wall portions 312A,312A, . . . is disposed side by side in the axial direction (D1direction) of the shaft member 20A at intervals. A plurality of voidportions 313A, 313A, . . . is provided between the plurality of sidewall portions 312A, 312A, . . . . The void portion 313A has a width (D1direction) of, for example, 5 μm or more and 200 μm or less. As anexample, in a case where the base portion 31A is formed of Al₂O₃, thewidth (D1 direction) of the void portion 313A is 57 μm.

In the present embodiment, the plurality of side wall portions 312A,312A, . . . is formed of a plurality of fins disposed side by side inthe axial direction (D1 direction) of the shaft member 20A. That is, theside wall portion 312A as the fin forms a protrusion portion in thethree-dimensional uneven structure, and the void portion 313A betweentwo side wall portions 312A and 312A forms a recess portion in thethree-dimensional uneven structure.

The reflection portion 32A is formed on the main surface 311Aa of theupper wall portion 311A and formed across all of the main surface 311Aa.The reflection portion 32A has a thickness (D3 direction) of, forexample, 50 nm or more and 500 nm. As an example, the thickness of thereflection portion 32A is 200 nm. The dynamic deformation amount in thethickness direct on of the reflection portion 32A (the maximum bendingamount δ in the D3 direction) is, for example, 70 nm or less.

The reflection portion 32A has a reflection surface 32Aa that reflectslaser light radiated from the outside. The reflection surface 32Aa is aflat surface parallel to the main surface 311Aa of the upper wallportion 311A. This reflection portion 32A is formed of, for example, ametal. The metal is not particularly limited and is, for example,aluminum (Al).

The reflection portion 32A preferably has a large thickness (D3direction) and a small diameter (distance from a rotation axis) so as toprevent dynamic deformation as much as possible. In particular, dynamicdeformation quintically changes relative to a change in diameter, andthus a slight increase in diameter causes significant dynamicdeformation. Therefore, the diameter of the reflection portion 32 is oneof extremely important parameters for the mirror device 1A.

In addition, the rotation angle of the reflection member 30A is limitedto a range in which stress generated by rotation does not cause thebreakage of the shaft member 20. Under a constant torque and a constantoperation resonant frequency, an optical scanning angle is inverselyproportional to the moment of inertia of the reflection member 30A.Therefore, it is necessary to decrease the moment of inertia of thereflection member 30A in order to increase the optical scanning angle.The moment of inertia around the rotation axis is generally proportionalto the mass and the square of the radius of rotation, and thus, when thewidth (D2 direction) of the reflection member 30A is decreased, theoptical scanning angle can be increased. However, in order to realize ahorizontal resolution of 1,920, which is as high as that of HDTVs, at anoperation resonant frequency of 40 kHz, it is necessary to increase thediameter (D3 direction) of the reflection portion 32 while suppressingan increase in the moment of inertia as much as possible.

Therefore, as an example of the conditions of the mirror device 1A, forexample, an operation frequency of 40 kHz or more, an optical scanningangle of 60 degrees or more (a rotation angle of 15 degrees or more), adiameter (D2 direction) of the reflection portion 32A of 2 mm or more,and a dynamic deformation of 70 nm or less are assumed. In a case wherethe deformation amount in the thickness direction (D3 direction) of thereflection portion 32A is set to less than 70 nm (FIG. 2), under theabove-described conditions showing the performance of the mirror device1A, the width of the side wall portion 312 that supports the reflectionportion 32A and the intervals between two adjacent side wall portions312A and 312A are determined. For example, in a case where a materialforming the base portion 31A is alumina (Al₂O₃) and the upper wallportion 311A is set to be thin enough to have no influence on thestrength of the base portion 31A, it is possible to set the thickness(D3 direction) of the reflection portion 32A to 1 μm, the width (D3direction) of the side wall portion 312A to 679 μm, the thickness (D2direction) of the side wall portion 312A to 84 nm, and the width of thevoid portion 313A between two adjacent side wall portions 312A and 312Ato 57 μm. In such a case, the reflection member 30A increases indiameter and decreases in weight, and an increase in the moment ofinertia of the reflection member 30A is suppressed. Furthermore, thedynamic deformation amount in the thickness direction (D3 direction) ofthe reflection portion 32A is sufficiently suppressed, the flat surfacestate of the reflection surface 32Aa of the reflection portion 32A ismaintained during the swinging of the reflection member 30A, and it ispossible to suppress the interference of reflected light or thedeformation of a spot pattern.

The material forming the base portion 31A may be a material other thanalumina. Even in such a case, it is possible to determine the thicknessof the reflection portion 32A, the width and thickness of the side wallportion 312A, and the width of the void portion 313A between twoadjacent side wall portions 312A and 312A on the basis of the propertyvalues such as density of the material so that the above-describedconditions of the mirror device 1A are satisfied.

The mirror device 1A of FIG. 1 can be manufactured using, for example,the following method. A silicon layer of a silicon wafer (SOI wafer orthe like) is deep-etched, and an ALD layer and/or an MLD layer aredeposited on an uneven portion formed by the deep etching. Next, throughgrooves are formed on part of the upper surfaces of protrusion portionsby etching, and then part of the silicon layer is etched as a sacrificelayer through the through grooves. The mirror device 1A can be obtainedby repeating a series of the above-described steps. In addition, themirror device 1A can also be manufactured using a manufacturing methoddescribed below.

As described above, according to the present embodiment, the baseportion 31A has a three-dimensional uneven structure including the upperwall portion 311A (bottom wall portion) having a main surface providedalong the axial direction (D1 direction) of the shaft member 20A and theplurality of side wall portions 312A, 312A, . . . extending from theupper wall portion 311A on the side opposite to the reflection portion32A, and thus it is possible to suppress the dynamic deformation of thereflection portion 32A while increasing the operation frequency, theoptical scanning angle, and the diameter of the reflection member to belarger than in the related art, and it is possible to improve theresolution of scanning laser devices.

FIG. 3 is a perspective view schematically showing a configuration of amirror device according to a second embodiment of the presentdisclosure. FIG. 4A is a plan view of the mirror device of FIG. 3, andFIG. 4B is a cross-sectional view in a direction of a line I-I in FIG.4A. FIG. 5 is a partial enlarged plan view of FIG. 4A.

As shown in FIG. 3 and FIG. 4A, a mirror device 1B includes a frame body10B, a shaft member 20B provided inside the frame body 10B and connectedto the frame body 10B, a reflection member 30B fixed to the shaft member20B and provided so as to be capable of swinging around an axis of theshaft member 20B, and a pair of comb tooth portions 40Ba and 40Bbprovided in the frame body 10B.

The frame body 10B in the present embodiment is disposed along thein-plane direction that is regulated by the D1 direction and the D2direction and has a substantially rectangular shape in a plan view ofthe mirror device 1B. The frame body 10B has a length (D1 direction) of200 μm or more and 10,000 μm or less and a width (D2 direction) of 100μm or more and 5,000 μm or less. As an example, the frame body 10B is4,400 μm in length and 2,600 μm in width. The frame body 10B is, forexample, formed of a silicon (Si) layer, formed of a laminate of asilicon layer and an oxide layer, or formed of a germanium (Ge) layer.The silicon layer is formed of, for example, single-crystal silicon(Si), and the oxide layer is formed of, for example, silicon oxide(SiO₂or the like).

The shaft member 20B has a first shaft portion 20Ba that couples,between a pair of facing frame portions 10Ba and 10Bb, the frame portion10Ba and the reflection member 30B, a second shaft portion 20Bb thatcouples the frame portion 10Bb and the reflection member 30B, and athird shaft portion 20Bc that passes through the center of thereflection member 30B and is connected to the first shaft portion 20Baand the second shaft portion 20Bb. The shaft member 20B has asubstantially square shape in a cross section in the width direction (D2direction). The shaft member 20B has, for example, a length (D1direction) of 200 μm or more and 12,000 μm or less and a width (D2direction) of 5 μm or more and 300 μm or less. As an example, the shaftmember 20B is 4,400 μm in length and 24 μm in width.

The shaft member 20B is integrally formed with a base portion 31B,described below, of the reflection member 30B. However, theconfiguration is not limited thereto, and the shaft member 20B mayfurther have a rod-shaped member disposed in the shaft center of theshaft member 20B as a skeleton. In such a case, the stiffness of theshaft member 20B against notation increases, and a larger opticalscanning angle can be stably obtained. In addition, the width of thethird shaft portion 20Bc is larger than the widths of the first shaftportion 20Ba and the second shaft portion 20Bb, but these widths may bethe same as each other.

The shaft member 20B is, for example, formed of a silicon (Si) layer,formed of a laminate of a silicon layer and an oxide layer, or formed ofa germanium (Ge) layer. The silicon layer is formed of, for example,single-crystal silicon or polycrystal silicon, and the oxide layer isformed of, for example, silicon oxide (SiO₂ or the like).

As shown in FIG. 4B, the reflection member 30B has a base portion 31Bprovided along the axial direction (D1 direction) of the shaft member20B and a reflection portion 32B provided on the base portion 31B. Thisbase portion 31B has a three-dimensional uneven structure including abottom wall portion 311B having a main surface 311Ba provided along theaxial direction (D1 direction) of the shaft member 20B and a pluralityof side wall portions 312B, 315B, . . . extending from the bottom wallportion 311B on the side opposite to the reflection portion 32B.

The plurality of side wall portions 312B, 312B, . . . is disposed sideby side in the axial direction (D1 direction) of the shaft member 20B atintervals. A plurality of void portions 313B, 313B, . . . is providedbetween the plurality of side wall portions 312B, 312B, . . . .

Specifically, the base portion 31B in the present embodiment includesthe bottom wall portion 311B, a first side wall portion group 312BBformed of a plurality of pairs of first side wall portions 312Ba and312Bb extending in a first direction (D2 direction) in a plan view ofthe base portion 31B, and a first upper wall portion group 314BB formedof a plurality of first upper wall portions 314B that couples the pairsof first side wall portions 312Ba and 312Bb. In addition, in the presentembodiment, the base portion 31B further includes a pair of second sidewall portions 315Ba and 315Bb disposed so as to surround the first sidewall portion group 312BB in the plan view of the base portion 31B and asecond upper wall portion 316B that couples the pair of second sidewallportions 315Ba and 315Bb and is connected to the first upper wallportion group 314BB.

That is, in the present embodiment, the bottom wall portion 311B, thepair of first side wall portions 312Ba and 312Bb, and a first upper wallportion 314B that defines a first hollow portion 317B form a protrusionportion in the three-dimensional uneven structure. In addition, thebottom wall portion 311B, the pair of second side wall portions 315Baand 315Bb, and the second upper wall portion 316B that defines a secondhollow portion 318B form another protrusion portion in thethree-dimensional uneven structure. In addition, the void portion 313Bbetween two adjacent first side wall portions 312Ba and 312Bb form arecess portion in the three-dimensional uneven structure.

The base portion 31B is a member that supports the reflection portion32B and swings clockwise or counterclockwise due to stress generated bythe torsion of the shaft member 20B. As described above, this baseportion 31B is integrally formed with the shaft member 20B. The baseportion 31B has a substantial disc shape and has a diameter of 100 μm ormore and 5,000 μm or less and a height (D3 direction) of 10 μm or moreand 2,000 μm or less. As an example, the base portion 31B is 2,000 μm indiameter and 90 μm in height.

The base portion 31B is preferably formed of an ALD layer and/or an MLDlayer. In such a case, it is possible to reliably realize a high aspectratio of the side wall portion 312B.

The base portion 31B in the present embodiment is formed by a dryprocess of ALD and/or MLD, but the method is not limited thereto. Thebase portion may be formed by other dry process such as LP-CVD with acondition of the obtainment of the above-described high aspect ratio.

The base portion 31B can be formed of any of a metal oxide and/or ametal nitride and is preferably formed of a metal oxide. The metal oxideis not particularly limited and is, for example, aluminum oxide (Al₂O₃).The metal nitride is, for example, silicon nitride (SiN or Si₃N₄).

The bottom wall portion 311B has a substantially circular shape in theplan view of the base portion 31B and is formed across all of the baseportion 31B in the plan view of the base portion 31B. The bottom wallportion 311B has a thickness (D3 direction) of 20 nm or more and 500 nmor less. As an example, the thickness of the bottom wall portion 311B is100 nm. The reflection portion 32B is formed on one main surface 311Baof the bottom wall portion 311B, and the plurality of side wall portions312B, 312B, . . . is provided on the other main surface 311Bb.

The pairs of first side wall portions 312Ba and 312Bb are disposedperpendicular to the bottom wall portion 311B and have a substantiallyrectangular shape in the side view in the D1 direction. Each of thepairs of first side wall portion 312Ba and 312Bb has, for example, alength (D2 direction) of 100 μm or more and 5,000 μm or less, a width(D3 direction) of 10 μm or more and 2,000 μm or less, and a thickness(D1 direction) of 20 nm or more and 500 nm or less. The ratio of theheight to the thickness of each of the pairs of first side wall portion312Ba and 312Bb (the aspect ratio of the D3-direction dimension to theD1-direction dimension) is 20 or more and 100,000 or less, preferably100 or more and 10,000 or less, more preferably 500 or more and 5,000 orless, particularly preferably 800 or more and 1,200 or less, and each ofthe pairs of side wall portions has a characteristic high aspect ratio.As an example, each of the pairs of first side wall portion 312Ba and312Bb is 2,000 μm in length, 90 μm in width, and 100 nm in thickness. Inthis case, the aspect ratio of each of the pairs of first side wallportions 312Ba and 312Bb is 900.

The first upper wall portion 314B is long in a plan view in the D3direction (FIG. 5). The first upper wall portion 314B has, for example,a width (D1 direction) of 30 μm or more and 70 μm or less and athickness (D3 direction) of 20 nm or more and 500 nm or less. As anexample, the first upper wall portion 314B is 65 μm in width and 100 nmin thickness. In a case where the width of the first upper wall portion314B is sufficiently wide, it is possible to reliably form a throughhole described below in the first upper wall portion 314B.

The pair of second side wall portions 315Ba and 315Bb has asubstantially annular shape in the plan view in the D3 direction. Thepair of second side wall portions 315Ba and 315Bb has, for example, awidth (D3 direction) of 10 μm or more and 2,000 μm or less and athickness (D1 direction) of 20 nm or more and 500 nm or less. The pairof second side wall portions 315Ba and 315Bb has an aspect ratio as highas that of the pair of first side wall portions 312Ba and 312Bb. As anexample, the pair of second side wall portions 315Ba and 315Bb is 90 μmin width, 100 nm in thickness, and 900 in aspect ratio. The annular pairof second side wall portions 315Ba and 315Bb being coupled with theplurality of pairs of first side wall portions 312Ba and 312Bb improvesthe stiffness of the base portion 31B.

The second upper wall portion 316B has a substantially annular shape inthe plan view in the D3 direction (FIG. 4B). The second upper wallportion 316B has, for example, a width of 30 μm or more and 70 μm orless and a thickness (D3 direction) of 20 nm or more and 500 nm or less.As an example, the second upper wall portion 316B is 65 μm in width and100 nm in thickness. In a case where the width of the second upper wallportion 316B is sufficiently wide, it is possible to reliably form athrough hole described below in the second upper wall portion 316B.

In each of the first upper wall portion 316Ba and the second upper wallportion 316B, as shown in FIG. 5, a plurality of through holes 319, 319,. . . is provided. In the present embodiment, the plurality of throughholes 319 and 319 is formed along a longitudinal direction (D2direction) of the first upper wall portion 314B at equal intervals. Inaddition, the plurality of through holes 319, 319, . . . is formed alonga circumferential direction of the second upper wall portion 316B atequal intervals. The through hole 319 has, for example, an innerdiameter of 10 μm or more and 50 μm or less. As an example, the innerdiameter of the through hole 319 is 30 μm. One or a plurality of thethrough holes 319 may be provided in at least one of the first upperwall portion 316Ba and the second upper wall portion 316B.

In the present embodiment, the bottom wall portion 311B, the pair offirst side wall portions 312Ba and 312Bb, and the first upper wallportion 314B define the first hollow portion 317B. In addition, thebottom wall portion 311B, the pair of second side wall portions 315Baand 315Bb, and the second upper wall portion 316B define the secondhollow portion 318B. The formation of the through holes 319 having asufficient opening area in the first upper wall portion 314B enables thereliable formation of the first hollow portion 317B by isotropic etchingdescribed below. In addition, the formation of the through holes 319having a sufficient opening area in the second upper wall portion 316Benables the reliable formation of the second hollow portion 318B by theisotropic etching described below.

The reflection portion 32B is formed on the main surface 311Ba of thebottom wall portion 311B and formed across all of the main surface311Ba. The reflection portion 32B has a thickness (D3 direction) of, forexample, 0.05 μm or more and 1 μm. As an example, the thickness of thereflection portion 32B is 0.2 μm. The dynamic deformation amount in thethickness direction of the reflection portion 32B (the maximum bendingamount in the D3 direction) is preferably as small as possible and is,for example, 70 nm or less.

The reflection portion 32B has a reflection surface 32Ba that reflectslaser light radiated from the outside. The reflection surface 32Ba is aflat surface parallel to the main surface 311Ba of the bottom wallportion 311B. This reflection portion 32B is formed of, for example, ametal. The metal is not particularly limited and is, for example,substantially aluminum (Al).

The pair of comb tooth portions 40Ba and 40Bb is provided in anotherpair of facing frame portions 10Bc and 10Bd and extends in a direction(D2 direction) perpendicular to the axial direction (D1 direction) inthe plan view of the mirror device 1B. One comb finger forming the pairof comb tooth portions 40Ba and 40Bb has, for example, a length (D2direction) of 100 μm or more and 500 μm or less and a width (D1direction) of 10 μm or more and 40 μm or less. As an example, the combfinger is 300 μm in length and 25 μm in width. Another pair of combtooth portions is provided near (for example, below) the pair of combtooth portions 40Ba and 40Bb, and the frame body 10B swings by, forexample, an electromagnetic driving method. Due to this swing of theframe body 10B, the reflection member 30 oscillates in antiphaserelative to the frame body 10B.

When the above-described conditions described in the first embodimentare taken into account, in a case where a material forming the baseportion 31B is alumina (Al₂O₃), it is possible to set the thickness (D3direction) of the reflection portion 32B to 0.2 μm, the widths (D3direction) of the pair of first side wall portions 312Ba and 312Bb andthe pair of second side wall portions 315Ba and 315Bb to 90 μm, thethicknesses (D1 direction) of the pair of first side wall portions 312Baand 312Bb and the pair of second side wall portions 315Ba and 315Bb to100 nm, and the width of the void portion 313B between two adjacentfirst side wall portions 312Ba and 312Bb to 40 μm. The reflection member30B increases in diameter and decreases in weight, an increase in themoment of inertia of the reflection member 30B is suppressed, andfurthermore, the dynamic deformation in the thickness direction (D3direction) of the reflection portion 32B is sufficiently suppressed.Therefore, the flat surface state of the reflection surface 32Ba of thereflection portion 32B is maintained during the swinging of thereflection member 30B, and it is possible to suppress the interferenceof reflected light or the deformation of a spot pattern.

The material forming the base portion 31B may be a material other thanalumina. Even in such a case, it is possible to determine the thicknessof the reflection portion 32B, the widths and thicknesses of the pair offirst side wall portions 312Ba and 312Bb and the pair of second sidewall portions 315Ba and 315Bb, and the width of the void portion 313Bbetween two adjacent first side wall portions 312Ba and 312Bb on thebasis of the property values such as density of the material so that theabove-described conditions of the mirror device 1B are satisfied.

Next, an example of a method for manufacturing the mirror device 1B ofFIG. 3 will be described with reference to FIG. 6A to FIG. 10C. Themethod for manufacturing the mirror device 1B according to the presentembodiment has the following step (A1) to step (J1).

First, a mask M1 is formed in a predetermined shape on a device layer101 of an SOI wafer 100 (FIG. 6A), and then anisotropic deep reactiveion etching (RIE) is carried out on the device layer 101 of the SOIwafer 100, thereby forming an uneven portion 101 a extending in adirection perpendicular to a main surface of the SOI wafer 100 (FIG. 6B,step (A1)).

The three-dimensional uneven structure of the present disclosure isformed of a thin layer having a high aspect ratio, and thus the etchingspeed of the device layer 101 which is a sacrifice layer (target layer)is preferably fast, and the etching speed ratio between the device layer101 and an ALD layer described below is preferably 10,000:1 or more. Forexample, in a case where an etching gas is sulfur hexafluoride (SF₆),the etching speed ratio is 70,000.

Due to the present step, a plurality of slit-shaped groove portions 101b, 101 b, . . . is formed in the device layer 101 of the SOI wafer 100.In addition, a pair of comb tooth portions 202 a and 202 b may be formedon both sides of the uneven portion 101 a in addition to the unevenportion 101 a.

Next, a first layer 201A is conformally deposited on the uneven portion101 a by ALD (FIG. 6C, step (B1)). In ALD, it is possible to coat thesurface exposed by the deep etching without generating any uncoveredregions, and it is possible to uniformly deposit the first layer 201A ona surface of the uneven portion 101 a having the groove portions 101 bwith a high aspect ratio. In addition, from the viewpoint of thestiffness of a finally obtained three-dimensional uneven structure, thefirst layer 201A is more preferably formed by a dry process such as ALDthan a wet process.

Specifically, as shown in FIG. 7, a film formation raw material(precursor) is adsorbed to the surface of the uneven portion 101 a ofthe device layer 101 under a vacuum atmosphere. As the film formationmaterial, for example, methyl aluminum (TMA) is an exemplary example.After purging, a reaction active species is supplied, and the filmformation material and the reaction active species are reacted with eachother. As the reaction active species, for example, water vapor (H₂O) isan exemplary example. After that, purging is carried out again, and asingle atomic layer or a plurality of atomic layers is formed. In such acase, the first layer 201A can be laminated in increments of one atomiclayer, and, for example, in a case where the first layer 201A is formedof aluminum oxide (Al₂O₃), it is possible to laminate the first layer inincrements of one angstrom in thickness.

These layers are laminated by carrying out this cycle a number of times,and the first layer 201A is formed on a bottom surface 101 aa, a sidesurface 101 ab, and an upper surface 101 ac of the uneven portion 101 a.In addition, a first layer 201B is formed on the handle layer 102 of theSOI wafer 100. The first layers 201A and 201B are formed of, forexample, aluminum oxide. After the formation of the layers, an annealingtreatment is preferably carried out on the first layer 201A.

In order to realize a high aspect ratio of the side wall portion, aselection ratio (selectivity) is preferably high. The selection ratio isrepresented by the ratio (speed ratio) of the etching speed of amaterial forming a sacrifice layer to the etching speed of a materialforming a layer structure and is preferably 10,000 or more. For example,in a case where the sacrifice layer is silicon and the three-dimensionaluneven structure is aluminum oxide, the selection ratio of silicon toaluminum oxide is 70,000. According to a combination of theabove-described materials, an extremely high selectivity can beobtained, and it becomes possible to realize a high aspect ratio (forexample, 8,000).

In the present embodiment, the first layers 201A and 201B areconformally deposited by ALD, but the method is not limited thereto, andthe first layers 201A and 201B may be conformally deposited on theuneven portion 101 a by MLD. In MLD, a single molecular layer or aplurality of molecular layers is formed, these layers are laminatedtogether by carrying out this cycle a number of times, and the firstlayers 201A and 201B are formed. Alternatively, both an ALD layer and anMLD layer may be laminated on the uneven portion 101 a, and both layersmay be conformally deposited on the uneven portion 101 a.

In addition, in the present embodiment, the first layers 201A and 201Bare formed by the processes of ALD and/or MLD, but the method is notlimited thereto, and the first layers 201A and 201B may be formed byother processes such as LP-CVD with a condition of the obtainment of theabove-described high aspect ratio.

Next, a mask M2 such as a film resist having a predetermined resistpattern is formed on the device layer 101 of the SOI wafer 100 (FIG.8A), and a through hole 203 is formed in the first layer 201A formed onthe upper surface 101 ac of the uneven portion 101 a by anisotropicetching in which fast atom beams (FAB) or the like are used (FIG. 8B,step (C1)).

After that, a mask M3 is formed in a predetermined shape on a handlelayer 102 of the SOI wafer 100, and the first layer 201B formed on thehandle layer 102 is patterned by anisotropic etching in which fast atombeams (FAB) or the like are used (FIG. 8C, step (D1)).

Next, the handle layer 102 of the SOI wafer 100 is removed byanisotropic etching, thereby exposing an oxide layer 103 of the SOIwafer 100 (FIG. 9A, step (E1)). At this time, a pair of comb toothportions 204 a and 204 b that is to serve as a counter electrode of thepair of comb tooth portions 202 a and 202 b may be formed by carryingout anisotropic deep reactive ion etching (RIE) on the handle layer 102.

After that, the oxide layer 103 of the SOI wafer 100 is removed byanisotropic RIE, thereby exposing a lower surface 101 ad of the unevenportion 101 a (FIG. 9B, step (F1)). At this time, the oxide layer 103may be removed across a portion from right below the comb tooth portion202 a to right below the comb tooth portion 202 b or only the oxidelayer 103 positioned right below the uneven portion 101 a may beremoved.

Next, a second layer 205A is conformally deposited on the first layer201A and the lower surface 101 ad of the uneven portion 101 a by ALD(FIG. 9C, step (G1)). In addition, due to the present step, a secondlayer 205B is formed in the through hole 203.

In the present embodiment, the second layers 205A and 205B areconformally deposited by ALD, but the method is not limited thereto, andthe second layers 205A and 205B may be conformally deposited by ALDand/or MLD. In addition, the second layers 205A and 205B may be formedby other processes such as LP-CVD.

In addition, a mask M4 such as a stated is disposed on the device layer101 of the SOI wafer 100 (FIG. 10A), and the second layer 205B formed inthe through hole 203 is removed by anisotropic etching, thereby forminga through hole 203 again in the first layer 201A (FIG. 10A, step (H1)).

Next, a metal is deposited on the second layer 205A from the handlelayer 102 side of the SOI wafer 100, thereby forming a third layer 206on the second layer 205A (FIG. 10B, step (I1)). The third layer 206 isformed of, for example, aluminum. The third layer 206 is formed on thesecond layer 205A by, for example, a deposition method. The reflectionportion 32B is formed from this third layer 206 (refer to FIG. 4B).

After that, the uneven portion 101 a of the device layer 101 is removedthrough the through hole 203 by isotropic RIE (FIG. 10C, step (J1)). Forexample, in a case where an etching gas is sulfur hexafluoride (SF₆), aF atom generated from SF₆ reacts with silicon (Si) forming the unevenportion 101 a to produce SiF₄ having a high vapor pressure, and SiF₄ isdischarged to the outside through the through hole 203. Therefore, ahollow portion 207 that is defined by the first layer 201A and thesecond layer 205A is formed. That is, due to the present step, the baseportion 31B including the bottom wall portion 311B, the first side wallportion group 312BB formed of the plurality of pairs of first side wallportions 312Ba and 312Bb, and the first upper wall portion group 314BBformed of the plurality of first upper wall portions 314B is formed(refer to FIG. 4B), whereby the mirror device 1B is obtained.

Furthermore, in the step (C1) (FIG. 8A and FIG. 8B), a portion of thefirst layer 201A formed on the upper surface 101 ac of the unevenportion 101 a may be removed by anisotropic etching in which fast atombeams (FAB) or the like are used, and a through groove may be formedalong an extension direction of the upper surface 101 ac so that all ofthe upper surface 101 ac is exposed. Therefore, portions of the firstlayer 201A formed on both side surfaces 101 ab and 101 ab of the unevenportion 101 a are separated from each other. In addition, the secondlayer formed in the through groove is removed by subsequent anisotropicetching to form a through groove again (step (I1)), and the unevenportion 101 a is removed through the through groove by isotropic RIE(step (J1)). Therefore, it is possible to obtain the mirror device 1Ahaving a plurality of side wall portions (for example, a plurality offins) (FIG. 1).

As described above, according to the present embodiment, the baseportion 31B includes the bottom wall portion 311B, the first side wallportion group 312BB formed of the plurality of pairs of first side wallportions 312Ba and 312Bb, and the first upper wall portion group 314BBformed of the plurality of first upper wall portions 314B, and thus itis possible to further suppress the dynamic deformation of thereflection member 30B while increasing the operation frequency, theoptical scanning angle, and the diameter of the reflection member 30B tobe larger than in the related art, and it is possible to further improvethe resolution of scanning laser devices.

FIG. 11A is a partial plan view showing a modification example of thebase portion 31B of FIG. 3. FIG. 11 is a cross-sectional view in adirection of a line II-II of FIG. 11A, and FIG. 11C is a cross-sectionalview in a direction of a line III-III of FIG. 11A. The sameconfiguration as the mirror device 1B of FIG. 3 will be given the samereference sign and will not be described again. In addition, materialsof individual configurational elements of a base portion of FIG. 11A arebasically the same as the materials of the respective configurationalelements of the base portion 31B of FIG. 3 and thus will not bedescribed again.

As shown in FIG. 11A to FIG. 11C, a base portion 31C has a plurality offirst shell-shaped structures S1, S1, . . . disposed in a matrix shapein a plan view of the base portion 31C and a plurality of second shellshaped structures S2, S2, . . . that is disposed in a matrix shape inthe plan view of the base portion 31C and couples the adjacent firstshell-shaped structures S1, S1, . . . . The first shell-shaped structureS1 defines a substantially quadratic prism-shaped void portion G1, andthe second shell-shaped structure S2 defines a substantially polygonalcolumn-shaped void portion G2. In addition, the plurality of firstshell-shaped structures S1, S1, . . . and the plurality of secondshell-shaped structures S2, S2, . . . are coupled to each other to forma single shell-shaped structure.

The first shell-shaped structure S1 has a plurality of first side wallportions 312C and 312C provided side by side in the first direction (D1direction) and third side wall portions 313C and 313C provided side byside in a second direction (D2 direction) intersecting the firstdirection. In addition, the second shell-shaped structure S2 has firstside wall portions 314C and 314C provided side by side in the firstdirection (D1 direction) and third side wall portions 315C and 315Cprovided side by side in the second direction (D2 direction)intersecting the first direction. That is, the base portion 31C in thepresent modification example has a three-dimensional uneven structureincluding the first side wall portions 312C and 314C and the third sidewall portions 313C and 315C (a plurality of side wall portions)extending from the bottom wall portion 311B on the side opposite to thereflection portion 32B.

Specifically, the base portion 31C includes a first side wall portiongroup 312CC formed of a bottom wall portion 311C and a plurality ofpairs of first side wall portions 312Ca and 312Cb extending in the firstdirection (D2 direction) in the plan view of the base portion 31C and athird side wall portion group 313CC formed of a plurality of pairs ofthird side wall portions 313Ca and 313Cb that extends in the seconddirection (D1 direction) intersecting the first direction and couplesthe pairs of first side wall portions 312Ca and 312Cb. In the presentmodification example, the first side wall portion group 312CC and thethird side wall portion group 313CC are disposed in a grid shape in theplan view of the base portion 31C.

In addition, the base portion 31C includes a first side wall portiongroup 314CC formed of a plurality of pairs of first side wall portions314Ca and 314Cb extending in the first direction (D2 direction) in theplan view of the base portion 31C and a third side wall portion group315CC formed of a plurality of pairs of third side wall portions 315Caand 315Cb extending in the second direction (D1 direction) intersectingthe first direction. In the present modification example, the first sidewall portion group 314CC and the third side wall portion group 315CC aredisposed in a grid shape in the plan view of the base portion 31C.

The base portion 31 includes a third upper wall portion group 316CCformed of a plurality of third upper wall portions 316C that is definedby two adjacent first side wall portions 312Ca and 312Cb and twoadjacent third side wall portions 315Ca and 315Cb in the plan view ofthe base portion 31C. A region surrounded by the bottom wall portion311C, the adjacent first side wall portions 312Ca and 312Cb, theadjacent third side wall portions 315Ca and 315Cb, and the third upperwall portion 316C forms a solid protrusion portion 317C.

In the third upper wall portion 316C, one or a plurality of throughholes, not shown, may be provided. In such a case, the region surroundedby the bottom wall portion 311C, the adjacent first side wall portions312Ca and 312Cb, the adjacent third side wall portions 313Ca and 315Cb,and the third upper wall portion 316C forms a third hollow portion. Insuch a case, it is possible to further reduce the weight of thereflection member 30C.

In addition, the base portion 31 includes a third upper wall portiongroup 318CC formed of a plurality of third upper wall portions 318C thatis defined by two adjacent first side wall portions 314Ca and 314Cb andtwo adjacent third side wall portions 313Ca and 313Cb in the plan viewof the base portion 31C (FIG. 11C). A region surrounded by the bottomwall portion 311C, the adjacent first side wall portions 314Ca and314Cb, the adjacent third side wall portions 313Ca and 313Cb, and thethird upper wall portion 318C forms a solid protrusion portion 319C.

In the third upper wall portion 318C, one or a plurality of throughholes, not shown, may be provided. In such a case, the region surroundedby the bottom wall portion 311C, the adjacent first side wall portions314Ca and 314Cb, the adjacent third side wall portions 313Ca and 313Cb,and the third upper wall portion 318C forms another third hollowportion. In such a case, it is possible to further reduce the weight ofthe reflection member 30C.

In the present modification example, for example, in the method formanufacturing a mirror device, the step (A) to the step (J) is regardedas one cycle, in the first cycle, the plurality of first shell-shapedstructures S1, S1 . . . is formed, and in the second cycle, theplurality of second shell-shaped structures S2, S2 . . . is formed.Therefore, it is possible to manufacture a mirror device having the baseportion 31C.

According to the present modification example, the base portion 31Cincludes the third side wall portion group 313CC formed of the pluralityof pairs of third side wall portions 313Ca and 313Cb that extends in thesecond direction (D1 direction) intersecting the first direction and thethird side wall portion group 315CC formed of the plurality of pairs ofthird side wall portions 315Ca and 315Cb extending in the seconddirection (D1 direction), and thus it is possible to further improve thestiffness of the base portion 31C against stress in the D3 direction,and it is possible to improve the stiffness of the base portion 31Cagainst stress in the in-plane direction that is regulated by the D1direction and the D2 direction.

FIG. 12A is a partial plan view showing another modification example ofthe base portion 31B of FIG. 3. FIG. 12B is a cross-sectional view in adirection of a line IV-IV of FIG. 12A, and FIG. 12C is a cross-sectionalview in a direction of a line V-V of FIG. 12A. Materials of individualconfigurational elements of a base portion of FIG. 12A are basically thesame as the materials of the respective configurational elements of thebase portion 31B of FIG. 3 and thus will not be described again.

As shown in FIG. 12A to FIG. 12C, a base portion 310 has a plurality ofthird shell-shaped structures S3, S3, . . . disposed in a matrix shapein a plan view of the base portion 31D. The third shell-shaped structureS3 defines a substantially triangular prism-shaped void portion G3.

Specifically, the base portion 31D includes the bottom wall portion311D, a first side wall portion group 312DD formed of a plurality ofpairs of first side wall portions 312Da and 312Db extending in the firstdirection (D2 direction) in the plan view of the base portion 31D, athird side wall portion group 313DD formed of a plurality of pairs ofthird side wall portions 313Da and 313Db extending in a second direction(D4 direction) intersecting the first direction, and a fourth side wallportion group 314DD formed of a plurality of pairs of fourth side wallportions 314Da and 314Db extending in a third direction (D5 direction)intersecting both the first direction and the second direction.

The first side wall portion group 312DD, the third side wall portiongroup 313DD, and the fourth side wall portion group 314DD form atruss-shaped structure in the plan view of the base portion 31D. Thatis, any of the pair of first side wall portions 312Da and 312Db, any ofthe pair of third side wall portions 313Da and 313Db, and any of thepair of fourth side wall portions 314Da and 314Db form three sides of atriangular shape in the plan view of the base portion 31D.

In the present modification example, any of the pair of adjacent firstside wall portions 312Da and 312Db, any of the pair of third sidewallportions 313Da and 313Db, and any of the pair of fourth side wallportions 314Da and 314Db are coupled to one another. In addition, thefirst side wall portion, the second side wall portion, and the thirdside wall portion forming three sides of a triangular shape are disposedso that the portions intersect each other at 60 degrees in the plan viewof the base portion 31D and form the third shell-shaped structure S3having a substantially equilateral triangular prism shape. In addition,this third shell-shaped structure S3 is used as a unit, and theplurality of third shell-shaped structures S3, S3, . . . is disposed ina matrix shape in the plan view of the base portion 31D. As describedabove, the plurality of third shell-shaped structures S3, S3, . . .forms a shell-shaped structure array.

In addition, the base portion 31D includes a fourth upper wall portion315D that is defined by the first side wall portion group 312DD, thethird side wall portion group 313DD, and the fourth side wall portiongroup 314DD in the plan view of the base portion 31D. The fourth upperwall portion 315D couples the first side wall portion group 312DD, thethird side wall portion group 313DD, and the fourth side wall portiongroup 314DD.

According to the present modification example, the base portion includesthe third side wall portion group 313DD formed of the plurality of pairsof third side wall portions 313Da and 313Db extending in the seconddirection (D4 direction) intersecting the first direction and the fourthside wall portion group 314DD formed of the plurality of pairs of fourthside wall portions 314Da and 314Db extending in the third direction (D5direction) intersecting both the first direction and the seconddirection, and thus it is possible to further improve the stiffness ofthe base portion 31D against stress in the D3 direction, and it ispossible to improve the stiffness of the base portion 31D against stressin the in-plane direction that is regulated by the D1 direction and theD2 direction.

FIG. 13A is a partial plan view showing another modification example ofthe base portion 31B of FIG. 3, and FIG. 13B is a cross-sectional viewin a direction of a line VI-VI of FIG. 13A. Materials of individualconfigurational elements of a base portion of FIG. 13A are basically thesame as the materials of the respective configurational elements of thebase portion 31B of FIG. 3 and thus will not be described again.

As shown in FIG. 13A and FIG. 13B, a base portion 31E has a plurality ofthird shell-shaped structures S4 which is a unit and a plurality ofthird shell-shaped structures S3 which is another unit. The plurality ofthird shell-shaped structures S4, S4, . . . is disposed in a matrixshape in a plan view of the base portion 31E, and the plurality of thirdshell-shaped structures S5, S5, . . . is also disposed in a matrix shapein a plan view of the base portion 31C. In addition, the plurality ofthird shell-shaped structures S4, S4, . . . and the plurality of thirdshell-shaped structures S5, S5, . . . are coupled to each other to forma single shell-shaped structure.

The third shell-shaped structure S4 defines a substantially triangularprism-shaped void portion G4, and the third shell-shaped structure S5defines a substantially polygonal column-shaped void portion G2. In thepresent modification example, the area of the third shell-shapedstructure S4 is smaller than the area of the third shell-shapedstructure S5 in the plan view of the base portion 31E, but is notlimited thereto and may be the same as the area of the thirdshell-shaped structure S5.

According to the present modification example, the plurality of thirdshell-shaped structures S4, S4, . . . and the plurality of thirdshell-shaped structures S5, S5, . . . are coupled to each other to forma single shell-shaped structure, and thus it is possible to furtherimprove the stiffness of the base portion 31E against stress in the D3direction, and it is possible to improve the stiffness of the baseportion 31E against stress in the in-plane direction that is regulatedby the D1 direction and the D2 direction.

FIG. 14A is a plan view showing a modification example of the mirrordevice 1B of FIG. 3, FIG. 14B is a cross-sectional view in a directionof a line VII-VII of FIG. 14A, and FIG. 14C is a cross-sectional view ina direction of a line VIII-VIII of FIG. 14A. In addition, FIG. 15A is anelectron microscope image of the mirror device of FIG. 14A, and FIG. 15Bis a partial cross-sectional image of FIG. 13A. Materials and functionsof individual configurational elements of a mirror device of the presentmodification example are basically the same as the materials andfunctions of the respective configurational elements of the mirrordevice 1B of FIG. 3 and thus will not be described again.

As shown in FIG. 14A, a mirror device 1F includes a frame body 10F, ashaft member 20F provided inside the frame body 10F and connected to theframe body 10F, a reflection member 30F fixed to the shaft member 20Fand provided so as to be capable of swinging around an axis of the shaftmember 20F, and a pair of comb tooth portions 40Fa and 40Fb provided inthe shaft member 20F.

The frame body 10F is disposed along the in-plane direction that isregulated by the D1 direction and the D2 direction and has asubstantially rectangular shape in a plan view of the mirror device 1F.The frame body 10F has a length (D1 direction) of 100 μm or more and5,000 μm or less and a width (D2 direction) of 100 μm or more and 5,000μm or less. As an example, the frame body 10F is 4,000 μm in length and3,000 μm in width.

The shaft member 20F has a first shaft portion 20Fa that couples,between a pair of facing frame portions 10Fa and 10Fb, the frame portion10Fa and the reflection member 30F and a second shaft portion 20Fb thatcouples the frame portion 10Fb and the reflection member 30F. The shaftmember 20F is integrally formed with, for example, a base portion 31F,described below, of the reflection member 30F. The shaft member 20F has,for example, a substantially rectangular shape in a cross-sectional viewin the width direction (D2 direction).

As shown in FIG. 14B and FIG. 14C, the reflection member 30F has thebase portion 31F provided along the axial direction (D1 direction) ofthe shaft member 20F and a reflection portion 32F provided on the baseportion. This base portion 31F has a three-dimensional uneven structureincluding a bottom wall portion 311F having a main surface 311Faprovided along the axial direction (D1 direction) of the shaft member20F and a first side wall portions 312F, a second side wall portion313F, and a second side wall portion 314F (a plurality of side wallportions) which extend from the bottom wall portion 311F on the sideopposite to the reflection portion 32F.

The base portion 31F is substantially a cuboid and has, for example, alength (D1 direction) of 100 μm or more and 5,000 μm or less, a width(D2 direction) of 100 μm or more and 5,000 μm or less, and a height (D3direction) of 10 μm or more and 2,000 μm or less. As an example, thebase portion 31F is 2,000 μm in length, 2,000 μm in width, and 679 μm inheight.

The base portion 31F includes a first side wall portion group 312FFformed of a bottom wall portion 311F and a plurality of pairs of firstside wall portions 312Fa and 312Fb extending in the first direction (D2direction) in the plan view of the base portion 31F, a third side wallportion group 313FF formed of a plurality of pairs of third side wallportions 313Fa and 313Fb extending in the second direction (D4direction) intersecting the first direction, a fourth side wall portiongroup 314FF formed of a plurality of pairs of fourth side wall portions314Fa and 314Fb extending in the third direction (D5 direction)intersecting both the first direction and the second direction, and afirst side wall portion group 312FF.

In the present modification example, similar to the modification exampleof FIG. 12A, the first sidewall portion group 312FF, the third side wallportion group 313FF, and the fourth side wall portion group 314FF form atruss-shaped structure in the plan view of the base portion 31F. Thatis, any of the pair of first side wall portions 312Fa and 312Fb, any ofthe pair of third side wall portions 313Fa and 313Fb, and any of thepair of fourth side wall portions 314Fa and 314Fb form three sides of atriangular shape in the plan view of the base portion 31F.

In addition, any of the pair of adjacent first side wall portions 312Faand 312Fb, any of the pair of third side wall portions 313Fa and 313Fb,and any of the pair of fourth side wall portions 314Fa and 314Fb arecoupled to one another. In the present modification example, the firstside wall portion, the second side wall portion, and the third side wallportion forming three sides of a triangular shape are disposed so thatthe portions intersect each other at 60 degrees in the plan view of thebase portion 31F and form the third shell-shaped structure S3 having asubstantially equilateral triangular prism shape. In addition, thisthird shell-shaped structure S3 is used as a unit, and the plurality ofthird shell-shaped structures S3, S3, . . . is disposed in a matrixshape in the plan view of the base portion 31F. As described above, theplurality of third shell-shaped structures S3, S3, . . . forms ashell-shaped structure array. In addition, the third shell-shapedstructure S3 defines a void portion G3 having a substantiallyequilateral triangular prism shape.

In addition, the base portion 31F includes a fourth upper wall portion315F that is defined by the first side wall portion group 312FF, thethird side wall portion group 313FF, and the fourth side wall portiongroup 314FF in the plan view of the base portion 31F. The fourth upperwall portion 315F is formed of a first portion 315Fa positioned betweenthe pair of first side wall portions 312Fa and 312Fb, a second portion315Fb positioned between the pair of third side wall portions 313Fa and313Fb, a third portion 315Fc positioned between the pair of fourth sidewall portions 314Fa and 314Fb, and a fourth portion 315Fd that the firstportion 315Fa, the second portion 315Fb, and the third portion 315Fc ofthe fourth upper wall portion 315F intersect (FIG. 14A to FIG. 14C).

In the fourth upper wall portion 315F, a plurality of through holes 319,319, . . . is provided. For example, in each of the first portion 315Fa,the second portion 315Fb, the third portion 315Fc, and the fourthportion 315Fd of the fourth upper wall portion 315F, the through holes319 are provided.

Furthermore, in the present modification example, the base portion 31Fhas a fourth hollow portion 317F formed of a first portion 317Fa, asecond portion 317Fb, a third portion 317Fc, and a fourth portion 317Fd(FIG. 14B, FIG. 14C, and FIG. 15B). The bottom wall portion 311F, thepair of first side wall portions 312Fa and 312Fb, and the first portion315Fa of the fourth upper wall portion 315F define the first portion317Fa of the fourth hollow portion 317F. Similarly, the bottom wallportion 311F, the pair of third side wall portions 313Fa and 313Fb, andthe second portion 315Fb of the fourth upper wall portion 315F definethe second portion 317Fb of the fourth hollow portion 317F. In addition,the bottom wall portion 311F, the pair of fourth side wall portions314Fa and 314Fb, and the third portion 315Fc of the fourth upper wallportion 315F define the third portion 317Fc of the fourth hollow portion317F. Furthermore, the fourth portion 317Fd of the fourth hollow portion317F is provided right below the fourth portion 315Fd that the firstportion 315Fa, the second portion 315Fb, and the third portion 315Fc ofthe fourth upper wall portion 315F intersect (FIG. 15A and FIG. 15B).The fourth portion 317Fd communicates the first portion 317Fa, thesecond portion 317Fb, and the third portion 317Fc together. That is, thefirst portion 317Fa, the second portion 317Fb, the third portion 317Fc,and the fourth portion 317Fd of the fourth hollow portion 317F areintegrally formed. The fourth hollow portion 317F provided in the baseportion 31F as described above enables the additional reduction of theweight of the reflection member 30C.

FIG. 16A is a view showing three-dimensional mapping obtained bycarrying out surface profiling using a white-light interferometer in themirror device 1F of FIG. 14A. FIG. 16B is a graph showing the heightdistribution along a cross section in a direction of a line VIIII-VIIIIof FIG. 16A.

As shown in FIG. 16A and FIG. 16B, in the reflection member 30F of themirror device 1F, when the shaft member 20F (position: 1,000 μm) isregarded as the center, displacement in the height direction increasesas the position moves away from the shaft member 20F along the widthdirection (D2 direction). The height of the shaft member 20F (position:1,000 μm) is approximately −0.8 μm, and the height of an outer edge(position: 0 μm or 2,000 μm) of the reflection member 30F isapproximately 0.5 μm, and thus the surface displacement of thereflection member 30F is approximately 1.3 μm. From this result, it isfound that a flat surface is formed in the reflection member 30F and thedynamic deformation amount in the thickness direction can be decreased.

According to the present modification example, the base portion includesthe third side wall portion group 313FF formed of the plurality of pairsof third side wall portions 313Fa and 313Fb extending in the seconddirection (D4 direction) intersecting the first direction and the fourthside wall portion group 314FF formed of the plurality of pairs of fourthside wall portions 314Fa and 314Fb extending in the third direction (D5direction) intersecting both the first direction and the seconddirection, and thus it is possible to further improve the stiffness ofthe base portion 31F against stress in the D3 direction, and it ispossible to improve the stiffness of the base portion 31F against stressin the in-plane direction that is regulated by the D1 direction and theD2 direction. In addition, the base portion 31F has the fourth hollowportion 317F, and thus it is possible to further reduce the weight ofthe reflection member 30F.

FIG. 17A is a plan view schematically showing a configuration of amirror device according to a third embodiment of the present disclosure,and FIG. 17B is a partial cross-sectional perspective view in adirection of a line X-X in FIG. 17A.

As shown in FIG. 17A, a mirror device 1G includes a frame body 10G, ashaft member 20G provided inside the frame body 10G and connected to theframe body 10G, a reflection member 30G fixed to the shaft member 20Gand provided so as to be capable of swinging around an axis of the shaftmember 20G, and a pair of comb tooth portions 40Ga and 40Gb provided inthe frame body 10G. Since the configurations of the frame body 10G, theshaft member 20G, and the pair of comb tooth portions 40Ga and 40Gb arethe same as the configurations of the frame body 10B, the shaft member20B, and the pair of comb tooth portions 40Ba and 40Bb in the mirrordevice 1B of FIG. 4 and thus will not be described again.

As shown in FIG. 17B, the reflection member 30G has a base portion 31Gprovided along the axial direction (D1 direction) of the shaft member20G and a reflection portion 32G provided on the base portion 31G. Thisbase portion 31G has a three-dimensional uneven structure including abottom wall portion 311G having a main surface 311Ga provided along theaxial direction (D1 direction) of the shaft member 20G and a pluralityof side wall portions 312G and 315G extending from the bottom wallportion 311G on the side opposite to the reflection portion 32G.

Specifically, the base portion 31G in the present embodiment includesthe bottom wall portion 311G, a first side wall portion group 312GGformed of a plurality of pairs of first side wall portions 312Ga and312Gb extending in a first direction (D2 direction) in a plan view ofthe base portion 31G, and a first upper wall portion group 314GG formedof a plurality of first upper wall portions 314G that couples the pairsof first side wall portions 312Ga and 312Gb. As shown in FIG. 17B, afirst upper wall portion 314Ga is provided with a plurality of throughholes 319, 319, . . . formed at equal intervals along the longitudinaldirection (D2 direction) of the first upper wall portion 314G. Inaddition, in the present embodiment, the base portion 31G furtherincludes a pair of second side wall portions, not shown, a second upperwall portion, and a plurality of through holes, not shown, provided inthe second upper wall portion. Since the configurations of the pair ofsecond side wall portions, the second upper wall portion, and thethrough hole are the same as the configurations of the pair of secondside wall portions 315Ba and 315Bb, the second upper wall portion 316B,and the through hole 319 in FIG. 4B and thus will not be describedagain.

The plurality of side wall portions 312G, 312G, . . . is disposed sideby side in the axial direction (D1 direction) of the shaft member 20G atintervals. In addition, in the present embodiment, the base portion 31Gfurther has a fifth side wall portion group 331GG that couples the firstside wall portions 312Ga and 312Gb adjacent to each other in a voidportion 313G between one of a pair of first side wall portions 312Ga and312Gb forming the first side wall portion group 312GG and one of anotherpair of first side wall portions 312Ga and 312Gb.

The fifth side wall portion group 331GG includes a plurality of fifthside wall portions 331G, and each of the plurality of fifth side wallportions 331G couples the first side wall portions 312Ga and 312Gbadjacent to each other. The fifth side wall portion 331G couples thefirst side wall portion 312Ga and the first side wall portion 312Gbadjacent to each other and is also coupled to the bottom wall portion311G.

In the present embodiment, the bottom wall portion 311G, the pair offirst side wall portions 312Ga and 312Gb, and the first upper wallportion 314G, which define a first hollow portion 317G, and the fifthside wall portion 331G form a protrusion portion in thethree-dimensional uneven structure. In addition, the void portion 313Gadefined by the bottom wall portion 311G, one of the pair of first sidewall portions 312Ga and 312Gb, and two fifth side wall portions 331G and331G adjacent to each other form a recess portion in thethree-dimensional uneven structure.

The base portion 31G is a member that supports the reflection portion32G and swings clockwise or counterclockwise due to stress generated bythe torsion of the shaft member 20G. As described above, this baseportion 31G is integrally formed with the shaft member 20G. The baseportion 31C has a substantial disc shape and has a diameter of 100 μm ormore and 5,000 μm or less and a height (D3 direction) of 10 μm or moreand 2,000 μm or less. As an example, the base portion 31G is 2,000 μm indiameter and 200 μm in height.

The base portion 31G is preferably formed of an ALD layer and/or an MLDlayer. In such a case, it is possible to reliably realize a high aspectratio of the side wall portion 312G.

The base portion 31G in the present embodiment is formed by a dryprocess of ALD and/or MLD, but the method is not limited thereto. Thebase portion may be formed by other dry process such as LP-CVD with acondition of the obtainment of the above-described high aspect ratio.

The base portion 31G can be formed of any of a metal oxide and/or ametal nitride and is preferably formed of a metal oxide. The metal oxideis not particularly limited and is, for example, aluminum oxide (Al₂O₃).The metal nitride is, for example, silicon nitride (SiN or Si₃N₄).

The bottom wall portion 311G has a substantially circular shape in theplan view of the base portion 310 and is formed across all of the baseportion 31G in the plan view of the base portion 31G. The bottom wallportion 311G has a thickness (D3 direction) of 20 nm or more and 500 nmor less. As an example, the thickness of the bottom wall portion 311G is100 nm. The reflection portion 32G is formed on one main surface 311Gaof the bottom wall portion 311G, and the plurality of side wall portions312G, 312G, . . . is provided on the other main surface 311Gb.

The pairs of first side wall portions 312Ga and 312Gb are disposedperpendicular to the bottom wall portion 311G and have a substantiallyrectangular shape in the side view in the D1 direction. Each of thepairs of first side wall portions 312Ga and 312Gb has, for example, alength (D2 direction) of 100 μm or more and 5,000 μm or less, a width(D3 direction) of 10 μm or more and 2,000 μm or less, and a thickness(D1 direction) of 20 nm or more and 500 nm or less. The ratio of theheight to the thickness of each of the pairs of first side wall portions312Ga and 312Gb (the aspect ratio of the D3-direction dimension to theD1-direction dimension) is 20 or more and 100,000 or less, preferably100 or more and 10,000 or less, more preferably 500 or more and 10,000or less, particularly preferably 800 or more and 10,000 or less. Thatis, each of the pairs of first side wall portions has a characteristichigh aspect ratio. As an example, each of the pairs of first side wallportion 312Ga and 312Gb is 2,000 μm in length, 200 μm in width, and 100nm in thickness. In this case, the aspect ratio of each of the pairs offirst side wall portions 312Ga and 312Gb is 2,000.

The first upper wall portion 314G is long in a plan view in the D3direction (FIG. 17B). The first upper wall portion 314G has, forexample, a width (D1 direction) of 30 μm or more and 70 μm or less and athickness (D3 direction) of 20 nm or more and 500 nm or less. As anexample, the first upper wall portion 314G is 65 μm in width and 100 nmin thickness. In a case where the width of the first upper wall portion314G is sufficiently wide, it is possible to reliably form a pluralityof through holes 319 in the first upper wall portion 314G.

FIG. 18 is an electron microscope image showing an example of theconfiguration of the plurality of fifth side wall portions 331G, 331G, .. . in FIG. 17B. As shown in FIG. 18, the plurality of fifth side wallportions 331G, 331G, . . . forms a wall-type structure in which thefirst side wall portion 312Ga and the first side wall portion 312Gbadjacent to each other are supported by a wall. The fifth side wallportion 331G extends in a direction intersecting the extension direction(D1 direction) of the first side wall portion 312Ga and the first sidewall portion 312Gb in a plan view of the base portion 31G. It ispreferable that the first side wall portion group 312GG and the fifthside wall portion group 331GG form a truss-shaped structure having atriangular shape as a configurational unit in the plan view of the baseportion 31G. In addition, the first side wall portion group 312GG andthe fifth side wall portion group 331GG may form a structural formhaving a trapezoidal shape as a configurational unit in the plan view ofthe reflection member 30B.

The fifth side wall portion 331G has, for example, a width (D3direction) of 10 μm or more and 2,000 μm or less and a thickness of 20nm or more and 500 nm or less. The fifth side wall portion 331G has anaspect ratio as high as that of the pair of first side wall portions312Ga and 312Gb. As an example, the pair of first side wall portions312Ga and 312Gb is 200 μm in width, 100 nm in thickness, and 2,000 inaspect ratio. The first side wall portion 312Ga and the first side wallportion 312Gb adjacent to each other are coupled by the fifth side wallportion 331G, whereby the rigidity of the base portion 31G,particularly, the rigidity of the base portion 31G in the in-planedirection, further improves.

Next, an example of a method for manufacturing the mirror device 1G ofFIG. 17A will be described with reference to FIG. 19A to FIG. 21C andFIG. 22A to FIG. 24. The method for manufacturing the mirror device 1Gaccording to the present embodiment has the following step (A2) to step(N2).

First, a first layer 301A is deposited on the device layer 101 of theSOI wafer 100 by ALD and/or MLD, and a second layer 301B is deposited onthe handle layer of the SOI wafer (FIG. 22A, step (A2)). The thicknessof the first layer 301A is, for example, 60 nm or more and 540 nm orless and is 180 nm as a specific example of the present embodiment. Thethickness of the second layer 301B is, for example, 60 nm or more and540 nm or less and is 180 nm as a specific example of the presentembodiment. The specific method of ALD and MLD is the same as that ofthe second embodiment and thus will not be described again.

Next, the first layer 301A is patterned by anisotropic etching, forwhich fast atom beams (FAB), ion milling, or the like are used, to forma plurality of linear protrusion portions 301Ab having a plurality ofcircular recess portions 301Aa linearly arranged on an upper surface anda plurality of linear recess portions 301Ac that allows the device layer101 to be exposed between the plurality of linear protrusion portions301Ab on the device layer 101 (FIG. 19A, step (B2)). In addition, thesecond layer 301B is patterned on the handle layer 102 by anisotropicetching (FIG. 19A, step (C2)).

As the patterning of the first layer 301A, for example, as shown in FIG.22B, the plurality of circular recess portions 301Aa is formed on thefirst layer 301A such that the plurality of circular recess portions301Aa is linearly arranged, and furthermore, the plurality of linearlyarranged circular recess portions 301Aa is formed at predeterminedintervals. Therefore, the plurality of circular recess portions 301Aa isformed on the matrix on the first layer 301A. The thickness of theplurality of circular recess portions 301Aa is, for example, 40 nm ormore and 360 nm or less and is 120 nm as a specific example of thepresent embodiment. Next, as shown in FIG. 22C, a linear portionincluding the plurality of linearly arranged circular recess portions301Aa is regarded as a configurational unit, and a portion between theconfigurational units adjacent to each other is removed to expose thedevice layer 101. Therefore, the plurality of linear recess portions301Ac and the plurality of linear protrusion portions 301Ab are formed.The thickness of the plurality of linear protrusion portions 301Ab isthe same as the thickness of the first layer 301A and is, for example,180 nm.

Next, masking is carried out on the linear recess portions 301Ac atpredetermined intervals, and anisotropic deep RIE (reactive ion etching)is carried out on the exposed device layer 101 on which the masking isnot carried out, thereby forming an uneven precursor 101AA including aplurality of first groove portions 101Aa extending in a directionperpendicular to the main surface of the SOI wafer 100 (FIG. 22D to FIG.22E, step (D2)).

For the formation of the uneven precursor 101AA, for example, a mask M5such as a film resist having a resist pattern in which a plurality ofholes having a trapezoidal shape or the like is disposed in a matrix isformed (FIG. 22D), and then anisotropic deep RIE is carried out. As aresult, in the plan view of the SOI wafer 100, the plurality of firstgroove portions 101Aa is formed in a matrix shape at positionscorresponding to the plurality of linear recess portions 301Ac (FIG.22E).

Next, a third layer 301C is conformally deposited on the unevenprecursor 101AA by ALD and/or MLD (step (E2)), and then a part of thethird layer 301C deposited on the upper surface of the portion on whichthe masking is carried out to the uneven precursor 101AA is removed byanisotropic etching (FIG. 22F, step (F2)). In addition, anisotropic deepRIE is carried out on the uneven precursor 101AA exposed by the removalof the part of the third layer 301C, and the portion exposed by theremoval of the part of the third layer 301C in the uneven precursor101AA is removed, thereby forming an uneven portion 101BA including aplurality of second groove portions 101Ba extending in a directionperpendicular to the main surface of the SOI wafer 100 (FIG. 23A, step(G2)). In addition, a fourth layer 301D is conformally deposited on theuneven portion 101BA by ALD and/or MLD (FIG. 23B, step (H2)).

Specifically, as shown in FIG. 24, the third layer 301C is formedthroughout all of the bottom surface, side surface, and upper surface ofthe uneven precursor 101AA by the conformal deposition of the thirdlayer 301C (for example, Al₂O₃ deposition). The thickness of the thirdlayer 301C is, for example, 40 nm or more and 360 nm or less and is 130nm as a specific example of the present embodiment.

In addition, in order to etch the uneven precursor 101AA (Si layer) inthe next step, the third layer 301C (Al₂O₃ layer) formed on the uppersurface of the uneven precursor 101AA is removed by anisotropic etchingin which fast atom beams (FAB) by Ar ions or the like are used. At thistime, it is preferable to irradiate the third layer 301C formed on theupper surface of the uneven precursor 101AA with atomic beams in a statein which the SOI wafer 100 is tilted with respect to the travelingdirection of the atomic beams. The angle θ of the SOI wafer 100 tiltedwith respect to the traveling direction of the atomic beams is, forexample, 15 to 80 degrees and is 60 degrees as an example of the presentembodiment.

The method for the irradiation with the atomic or ion beams is notparticularly limited. For example, the SOI wafer 100 is irradiated withatomic beams from the side of the SOI wafer 100 while the SOI wafer 100is rotated around an axis that passes through the central position ofthe SOI wafer 100 in the in-plane direction and is tilted with respectto the in-plane direction. With this method, at the time of removing thethird layer 301C formed on the upper surface of the uneven precursor101AA, it becomes difficult for atoms or ion beams to reach the thirdlayer 301C, which is to form the bottom wall portion 311G, (refer toFIG. 17B) compared with a case where the SOI wafer 100 is disposedperpendicular to the traveling direction of the atom or ion beams, andthe etching rate in the third layer 301C is controlled. As a result, itis possible to suppress the bottom wall portion 311G being thinned ordamaged. This anisotropic etching forms a state in which the third layer301C is formed on the bottom surface and the side surface of the unevenprecursor 101AA.

After that, the fourth layer 301D is conformally deposited after theremoval of the uneven precursor 101AA, whereby the fourth layer 301D isformed on the third layer 301C, and the fourth layer 301D is also formedon the surface exposed by removing the uneven precursor 101AA, that is,the side surface and the bottom surface on which the third layer 301C isnot formed. The thickness of the fourth layer 301D is, for example, 40nm or more and 360 nm or less and is 130 nm as a specific example of thepresent embodiment. As a result, the uneven portion 101BA including thethird layer 301C and the fourth layer 301D is formed right below thelinear recess portion 301Ac (FIG. 19B).

After that, the first layer 301A on the device layer 101 is patterned byanisotropic etching to expose a part of the device layer 101 in aportion other than the plurality of linear protrusion portions 301Ab andthe plurality of linear recess portions 301Ac (FIG. 19C), andanisotropic deep RIE is carried out on the exposed device layer 101(FIG. 19D). Due to the present step, a portion that is to form the outercontour of the reflection member 30G is formed on the device layer 101of the SOI wafer 100. At this time, a pair of comb tooth portions 402 aand 402 b may be formed on both sides of the part that is to form theouter contour of the reflection member 30G.

Next, the handle layer 102 of the SOI wafer 100 is removed byanisotropic etching, thereby exposing the oxide layer 103 of the SOIwafer 100 (FIG. 20A, step (H2)). At this time, a pair of comb toothportions 404 a and 404 b that is to serve as a counter electrode of thepair of comb tooth portions 402 a and 402 b may be formed by carryingout anisotropic deep RIE on the handle layer 102.

Next, the oxide layer 103 is removed by anisotropic RIE, therebyexposing a lower surface 101Bb of the uneven portion 101BA (FIG. 20B,step (J2)). At this time, the oxide layer 103 may be removed across theentire portion from right below the comb tooth portion 402 a to rightbelow the comb tooth portion 402 b or only the oxide layer 103positioned right below the uneven portion 101BA may be removed. Inaddition, a fifth layer 301E is conformally deposited on the lowersurface 101Bb of the uneven portion 101BA by ALD and/or MLD (FIG. 20C,step (K1)). In addition, due to the present step, the fifth layer 301Eis also formed over the first layer 301A to the fourth layer 301D.

After that, a mask, not shown, such as a stencil is disposed on thedevice layer 101 of the SOI wafer 100, and through holes 301Ad areformed at positions that correspond to the plurality of circular recessportions 301Aa of the first layer 301A by anisotropic etching (FIG. 21A,step (L2)). Therefore, as shown in FIG. 23C, the device layer 101 in thethrough holes 301Ad is exposed. In addition, in the present step, a maskM6 such as a stencil is disposed on the handle layer 102 side of the SOIwafer 100, and the fifth layer 301E formed on the lower surface of thedevice layer 101 and the fifth layer 301E formed on the lower surface ofthe handle layer 102 may be removed. Therefore, a connection surface fordisposing electrodes is formed, and it becomes possible to supply powerto the pair of comb tooth portions 402 a and 402 b and the pair of combtooth portions 404 a and 404 b through the electrodes.

Next, a metal is deposited on the fifth layer 301E from the handle layer102 side of the SOI wafer 100, thereby forming a sixth layer 302 on thefifth layer 301E (FIG. 21B, step (M2)). The sixth layer 302 is formedof, for example, aluminum. The sixth layer 302 is formed on the fifthlayer 301E by sputtering or the like with the mask M7 disposed on, forexample, the handle layer 102 side. The reflection portion 320 is formedfrom this sixth layer 302 (refer to FIG. 17B).

In addition, the uneven portion 101BA is removed through the throughholes 301Ad by isotropic RIE (FIG. 21C, step (N2)). As a result, asshown in FIG. 23D, hollow portions 303 defined by the first layer 301Aand the third layer 301C to the fifth layer 301E are formed. Thespecific method of the isotropic RIE is the same as that of the secondembodiment and thus will not be described again. Due to the presentstep, the base portion 31G including the bottom wall portion 311G, thefirst side wall portion group 312GG formed of the plurality of pairs offirst side wall portions 312Ga and 312Gb, the fifth side wall portiongroup 331GG formed of the plurality of fifth side wall portions 331G,and the first upper wall portion group 314GG formed of the plurality offirst upper wall portions 314G is formed (refer to FIG. 17B), wherebythe mirror device 1G is obtained.

Furthermore, in the step (B2) (FIC. 19A), instead of the plurality ofcircular recess portions 301Aa, linear recess portions that extend alongthe extension direction of the linear protrusion portions 301Ab may beformed on the upper surface of the linear protrusion portions 301Ab bypatterning the first layer 301A by anisotropic etching in which fastatom beams (FAB) or the like are used. In this case, through grooves areformed at positions that correspond to the plurality of linear recessportions in the first layer 301A (step (L2)), and the uneven portion101BA is removed through the through grooves by isotropic RIE (step(N2)). Therefore, it is possible to form a base portion 31 including thebottom wall portion 311G, the first side wall portion group 312GG formedof a plurality of pairs of first side wall portions 312Ga and 312Gb, andthe fifth side wall portion group 331GG formed of a plurality of fifthside wall portions 331G.

As described above, according to the present embodiment, since the baseportion 31G includes the bottom wall portion 311G, the first side wallportion group 312GG formed of the plurality of pairs of first sidewallportions 312Ga and 312Gb, the fifth side wall portion group 331GG formedof the plurality of fifth side wall portions 331G, and the first upperwall portion group 314GG formed of the plurality of first upper wallportions 314G, due to the disposition of the fifth side wall portiongroup 331GG, it is possible to still further suppress the dynamicdeformation of the reflection member 30G while further increasing theoperation frequency, the optical scanning angle, and the diameter of thereflection member 30G to the larger than in the related art andsuppressing an increase in the weight as much as possible, and it ispossible to significantly improve the resolution of scanning laserdevices.

In the present embodiment, in the plan view of the base portion 31G, theside wall portion 312G has a linear shape along the width direction (D2direction) of the shaft member 20G (FIG. 18), but the configuration isnot limited to this. For example, as shown in FIG. 25, the side wallportion 312G may have a continuous or discontinuous wave shape along thewidth direction of the shaft member 20G. In addition, the side wallportion 312G may have a curved shape at a portion positioned on the sideof the through hole 319, or the fifth side wall portion 331G may becoupled to the portion of the curved shape of the side wall portion 312G(the pair of first side wall portions 312Ga and 312Gb). Even with thepresent configuration, it is possible to still further suppress thedynamic deformation of the reflection member 30G.

FIG. 26 is a schematic view showing an example of a configuration of ascanning laser device according to a fourth embodiment of the presentdisclosure. In the present embodiment, a case where a scanning laserdevice is applied to a scanning laser display device will be describedas an example.

As shown in FIG. 17, a scanning laser device 2 includes a laser lightsource 3, the mirror device 1B, and a driving mechanism 4 that drivesthe mirror device 1B. This scanning laser device 2 is provided in, forexample, a scanning laser display device (scanning display), and animage is displayed on a screen panel P by scanning laser light L fromthe scanning laser device 2. In addition, the scanning laser device 2includes a control portion 5 that generally controls individualconfigurational elements in the device.

The laser light source 3 has three light emission elements correspondingto three primary colors of RGB and radiates laser light from these lightemission elements to the reflection member 30B of the mirror device 1B.The laser light is not particularly limited and is, for example, aparallel laser beam. Three laser light rays are multiplexed at, forexample, an optical waveguide or the like and output to the mirrordevice 1B.

The mirror device 1B is monoaxially or biaxially provided. In the caseof biaxially provided, the mirror device includes, for example, a framebody provided so as to capable of rotating and a reflection memberhaving a second rotation axis orthogonal to a first rotation axis of theframe body. In such a case, the laser light is scanned in the horizontaldirection and the vertical direction. Alternatively, two monoaxialmirror devices may be provided in the scanning laser device and disposedso that the two rotation axes thereof are orthogonal to each other. Inaddition, the mirror device is not limited to the mirror device 1B, andany or a plurality of the mirror devices 1A to 1F may be provided in thescanning laser device 2.

The driving mechanism 4 monoaxially or biaxially swings the reflectionmember 30B in the mirror device 1B by an electromagnetic driving method,an electrostatic driving method, or a piezoelectric driving method inwhich a comb tooth actuator is used. The driving mechanism 4 is capableof obtaining an operation resonant frequency by mechanically resonatingthe reflection member 30B in order to increase the optical scanningangle of the reflection member 30B. The reflection member 30B in themirror device 1B has a larger diameter and a lighter weight than thosein the related art, and the dynamic deformation amount in the thicknessdirection (D3 direction) of the reflection portion 32B is small, andthus it is possible to increase the operation resonant frequency to belarger than in the related art.

As described above, according to the present embodiment, the scanninglaser device 2 capable of realizing a high resolution than in therelated art is provided.

In addition, in the present embodiment, the scanning laser device 2includes the mirror device 1B, but the present disclosure is not limitedto this, and the scanning laser device may include the mirror device 1G.Even in this case, it is possible to realize a higher resolution than inthe related art.

Hitherto, the embodiments of the present disclosure have been describedin detail, but the present disclosure is not limited to theabove-described embodiments and can be transformed or modified in avariety of manners within the scope of the gist of the presentdisclosure described in claims.

INDUSTRIAL APPLICABILITY

The scanning laser device of the present disclosure can be applied to,for example, scanning laser display devices that are mounted in mobilephones, portable displays, wearable instruments, cars, ophthalmicinstruments, and the like. In addition, the scanning laser device canalso be applied to devices that not only scan screens or car windshieldsbut also scan retinas. Furthermore, the scanning laser device can beused not only for scanning laser display devices but also for industrialsensing, medical measurement, and the like. For example, it is possibleto apply the scanning laser device to, as an operation support system ofcars, scanning laser measurement instruments that measure the distancebetween a car and an object.

What is claimed is:
 1. A mirror device comprising: a frame body; a shaftmember provided inside the frame body and connected to the frame body;and a reflection member fixed to the shaft member and provided so as toswing around an axis of the shaft member, wherein the reflection memberhas a base portion provided along an axial direction of the shaft memberand a reflection portion provided on the base portion, and the baseportion has a three-dimensional uneven structure including a bottom wallportion having a main surface provided along the axial direction of theshaft member and a plurality of side wall portions extending from thebottom wall portion on a side opposite to the reflection portion.
 2. Themirror device according to claim 1, wherein a ratio of a height to athickness of the side wall portion is 20 or more and 100,000 or less. 3.The mirror device according to claim 1, wherein the base portion isformed of an ALD layer and/or an MLD layer.
 4. The mirror deviceaccording to claim 1, wherein the plurality of side wall portions isformed of a plurality of fins disposed at intervals in the axialdirection of the shaft member.
 5. The mirror device according to claim1, wherein the base portion includes the bottom wall portion, a firstside wall portion group formed of a plurality of pairs of first sidewall portions extending in a first direction in a plan view of the baseportion, and a first upper wall portion group formed of a plurality offirst upper wall portions that couples the pairs of first side wallportions.
 6. The mirror device according to claim 5, wherein the baseportion further includes a pair of second side wall portions disposed soas to surround the first side wall portion group in a plan view of thebase portion and a second upper wall portion that couples the pair ofsecond side wall portions and is connected to the first upper wallportion group.
 7. The mirror device according to claim 6, wherein athrough hole is provided in at least one of the first upper wall portionand the second upper wall portion, the bottom wall portion, the pair offirst side wall portions, and the first upper wall portion define afirst hollow portion, and the bottom wall portion, the pair of secondside wall portions, and the second upper wall portion define a secondhollow portion.
 8. The mirror device according to claim 1, wherein thebase portion includes the bottom wall portion, a first side wall portiongroup formed of a plurality of pairs of first side wall portionsextending in a first direction in a plan view of the base portion, and athird side wall portion group formed of a plurality of pairs of thirdside wall portions that extends in a second direction intersecting thefirst direction and couples the pairs of first side wall portions. 9.The mirror device according to claim 8, wherein the first side wallportion group and the third side wall portion group are disposed in agrid shape in a plan view of the base portion.
 10. The mirror deviceaccording to claim 9, wherein the base portion further includes a thirdupper wall portion group formed of a plurality of third upper wallportions that is defined by two adjacent first side wall portions andtwo adjacent third side wall portions in a plan view of the baseportion, one or a plurality of through holes is provided in the thirdupper wall portion, and the bottom wall portion, the pair of first sidewall portions, the pair of third side wall portions, and the third upperwall portion define a third hollow portion.
 11. The mirror deviceaccording to claim 1, wherein the base portion includes the first bottomwall portion, a first side wall portion group formed of a plurality ofpairs of first side wall portions extending in a first direction in aplan view of the base portion, a third side wall portion group formed ofa plurality of pairs of third side wall portions extending in a seconddirection intersecting the first direction, and a fourth side wallportion group formed of a plurality of pairs of fourth side wallportions extending in a third direction intersecting both the firstdirection and the second direction.
 12. The mirror device according toclaim 11, wherein the first side wall portion group, the third side wallportion group, and the fourth side wall portion group form atruss-shaped structure in a plan view of the base portion.
 13. Themirror device according to claim 12, wherein the base portion furtherincludes a fourth upper wall portion that is defined by the first sidewall portion group the third side wall portion group, and the fourthside wall portion group in a plan view of the base portion, one or aplurality of through holes is provided in the fourth upper wall portion,the bottom wall portion, the pair of first side wall portions, and afirst portion of the fourth upper wall portion define a first portion ofa fourth hollow portion, the bottom wall portion, the pair of third sidewall portions, and a second portion of the fourth upper wall portiondefine a second portion of the fourth hollow portion, and the bottomwall portion, the pair of fourth side wall portions, and a third portionof the fourth upper wall portion define a third portion of the fourthhollow portion.
 14. The mirror device according to claim 1, wherein thebase portion further includes a fifth side wall portion group thatcouples the first side wall portions adjacent to each other in a voidportion between one of a pair of first side wall portions forming thefirst side wall portion group and one of another pair of first side wallportions.
 15. The mirror device according to claim 14, wherein the firstside wall portion group and the fifth side wall portion group form atruss-shaped structure in a plan view of the base portion.
 16. Themirror device according to claim 1, further comprising: a pair of combtooth portions provided in any of the frame body and the shaft member.17. The mirror device according to claim 1, wherein the base portion isformed of a metal oxide.
 18. The mirror device according to claim 17,wherein the metal oxide is Al₂O₃.
 19. A scanning laser devicecomprising: a laser light source; the mirror device according to claim1; and a driving mechanism configured to drive the mirror device.
 20. Ascanning display comprising: the scanning laser device according toclaim
 19. 21. A method for manufacturing a mirror device comprising: astep (A1) of carrying out anisotropic deep reactive ion etching (RIE) ona device layer of an SOI wafer and forming in uneven portion extendingin a direction perpendicular to a main surface of the SOI wafer; a step(B1) of conformally depositing a first layer on the uneven portion byALD and/or MLD; a step (C1) of forming a through hole or a throughgroove in the first layer formed on an upper surface of the unevenportion by anisotropic etching; a step (D1) of patterning the firstlayer formed on a handle layer of the SOI wafer by anisotropic etching;a step (E1) of removing the handle layer of the SOI wafer by anisotropicetching to expose an oxide layer of the SOI wafer; a step (F1) ofremoving the oxide layer by anisotropic RIE to expose a lower surface ofthe uneven portion; a step (G1) of conformally depositing a second layeron the lower surface of the uneven portion by ALD and/or MLD; a step(H1) of removing the second layer formed in the through hole or thethrough groove by anisotropic etching to form a through hole or athrough groove in the first layer again; a step (I1) of depositing ametal on the second layer from the handle layer side of the SOI wafer toform a reflection portion on the second layer; and a step (J1) ofremoving the uneven portion of the device layer through the through holeor the through groove by isotropic RIE.
 22. A method for manufacturing amirror device comprising: a step (A2) of depositing a first layer on adevice layer of an SOI wafer by ALD and/or MLD and depositing a secondlayer on a handle layer of the SOI wafer; a step (B2) of patterning thefirst layer by anisotropic etching to form, on the device, a pluralityof linear protrusion portions having a plurality of circular recessportions linearly arranged on an upper surface and a plurality of linearrecess portions that allows the device layer to be exposed between theplurality of linear protrusion portions; a step (C2) of patterning thesecond layer on the handle layer by anisotropic etching; a step (D2) ofcarrying out masking on the linear recess portions at predeterminedintervals and carrying out anisotropic deep RIE (reactive ion etching)on the exposed device layer on which the masking is not carried out toform an uneven precursor including a plurality of first groove portionsextending in a direction perpendicular to a main surface of the SOIwafer; a step (E2) of conformally depositing a third layer on the unevenprecursor by ALD and/or MLD; a step (F2) of removing parts of the thirdlayer deposited on upper surfaces of portions on which the masking iscarried out in the uneven precursor by anisotropic etching; a step (G2)of carrying out anisotropic deep RIE on the uneven precursor exposed bythe removal of the parts of the third layer and removing the portionsexposed by the removal of the parts of the third layer in the unevenprecursor to form an uneven portion including a plurality of secondgroove portions extending in the direction perpendicular to the mainsurface of the SOI wafer; a step (H2) of conformally depositing a fourthlayer on the uneven portion by ALD and/or MLD; a step (I2) of removingthe handle layer of the SOI wafer by anisotropic etching to expose anoxide layer of the SOI wafer; a step (J2) of removing the oxide layer byanisotropic RIE to expose lower surfaces of the uneven portion; a step(K1) of conformally depositing a fifth layer on the lower surfaces ofthe uneven portion by ALD and/or MLD; a step (L2) of forming throughholes or through grooves at positions corresponding to the plurality ofcircular recess portions in the first layer by anisotropic etching; astep (M2) of depositing a metal on the fifth layer from the handle layerside of the SOI wafer to form a reflection portion on the fifth layer;and a step (N2) of removing the uneven portion through the through holesor the though grooves by isotropic RIE.